两类花岗岩的差异及其与钨成矿的关系

THE DIFFERENCES BETWEEN TWO TYPES OF GRANITOIDS AND THEIR RELATIONSHIPS WITH TUNGSTEN MINERALIZATION

同熔型和改造型两类花岗岩之间存在着一些差异:同熔型花岗岩类常为偏中酸性岩石; fo_2、氯和磷含量较高;和硼含量较低。改造型花岗岩常为偏酸性岩石;fo_2、氯和磷含量较低;氟和硼含量较高。根据钨的矿物-熔体和水热流体-熔体的分配实验结果来看,两类花岗岩的上述差异对钨的分配系数有较大的影响,表现为同熔型钨矿成矿岩体的钨总体分配系数和水热流体-熔体分配系数均大于改造型钨矿成矿岩体。这一结果可以解释两类花岗岩在岩浆演化与钨的富集、成矿岩体钨含量和钨矿化叠加等方面的差异。

There exist some differences between syntexis-and transformation-type granitoids, The syntexis-type granitoids associated with tungsten mineralization are more intermediate-acidic rocks. They have higher Cl and P contents and lower F and B contents with higher fo_2. The transformation-type granites are more acidic rooks. They have higher F and B contents and lower Cl and P contents with lower fo_2. Based on the experimental results of the partition for tungsten between mineral-granitic melt and between hydrothermal fluids-granitic melt, the abovementioned differences between the two types of granitoids have a strong influence on the partition coefficients for tungsten. Generally speaking, the syntexis-type granitoids associated with tungsten mineralizations have a larger bulk partition coefficient and partition coefficients between hydrothermal fluids-granitic melt for tungsten than the transformation-type granites. This result can be used to explain the differences between the two types of granitoids in the respects of magmatic evolution and tungsten enrichment, tungsten contents of the rocks related to tungsten mineralizations and superimposed tungsten mineralizations and so on.